ISSN:0002-9505    

DOI:10.1119/1.13806

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.13899

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.4755899

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

There are several hints in physics of a domain of external reality transcendent to three‐dimensional space and time. This paper calls attention to several of these intimations of a real world beyond the natural order. Examples are the complex state functions in configuration space of quantum mechanics, the singularity at the birth of the universe, the anthropic principle, the role of chance in evolution, and the unaccountable fruitfulness of mathematics for physics. None of these examples touch on the existence or activity of God, but they do suggest that external reality may be much richer than the natural world which it is the task of physics to describe.

ISSN:0002-9505    

DOI:10.1119/1.13901

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

Many physical systems are described by quadratic equations. In such cases the requirement for a real solution is that the discriminant be non‐negative. This requirement can often lead, directly or indirectly, to maximizing or minimizing some system variable of interest. Three examples suitable for a noncalculus physics course are given : (1) projectile motion, (2) hydrostatic equilibrium (Archimedes’ principle), and (3) resistance matching.

ISSN:0002-9505    

DOI:10.1119/1.13902

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

A detailed analysis is offered—with concomitant clarification, correction, and celebration—of the treatment in Newton’sPrincipiaof the external gravitational field produced by a spherically symmetric mass distribution. It is established, in particular, just how close thePrincipiacomes to achieving the most general result (whereby the sphere can be considered as concentrated at its center); it is also shown how thePrincipiaargument could easily have been extended so as to have gone the whole way.

ISSN:0002-9505    

DOI:10.1119/1.13903

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

An economic time‐to‐amplitude converter has been designed and built, able to measure time intervals of the order of milliseconds. Its main output is a positive signal proportional to the measured time, appropriate for a multichannel‐analyzer input. As an application we have measured the transit time Δtof a vertically falling Ping‐Pong ball across a small Δxgap, for different heights of release up to 17 m. The dependence of the speed Δx/Δton the fallen distance is well described by the model of air resistance proportional to the square of the instantaneous velocity. The measured terminal velocity is 9.5 m/s, 98% of which is attained after falling 12.5 m.

ISSN:0002-9505    

DOI:10.1119/1.13904

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

The Abraham‐Lorentz equation of motion for a charged particle admits ‘‘runaway’’ solutions which violate the law of inertia. The integrodifferential form of the Abraham–Lorentz equation eliminates the runaway solutions, but in so doing introduces ‘‘preacceleration’’ which violates the principle of causality. Here it is shown that there exists a form of the equation of motion for a nonrelativistic charged particle which is in accord with both the law of inertia and the principle of causality.

ISSN:0002-9505    

DOI:10.1119/1.13905

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

We  examine the motion of an Atwood’s Machine in which one of the masses is allowed to swing in a plane. Computer studies reveal a rich variety of trajectories. The orbits are classified (bounded, periodic, singular, and terminating), and formulas for the critical mass ratios are developed. Perturbative techniques yield good approximations to the computer‐generated trajectories. The model constitutes a simple example of a nonlinear dynamical system with two degrees of freedom.

ISSN:0002-9505    

DOI:10.1119/1.13791

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP

摘要:

It is shown that the simplest theory for the behavior of automobile tires under braking leads to an instability which causes the car to spin around in cars whose rear wheels lock before the front.

ISSN:0002-9505    

DOI:10.1119/1.13906

出版商:American Association of Physics Teachers    

年代:1984

数据来源: AIP